DESCRIPTION (Adapted from applicant's description): Sex determination is a fundamental process in human development. The predisposition to many diseases is affected by whether one is male or female. In addition, approximately one in every one thousand live-born infants has abnormal gonadal development (gonadal dysgenesis). Most commonly this occurs from absence of an SRY gene, mutation of the SRY gene, or failure to transmit the signal of the SRY gene, but in many cases, the genetic basis is not understood. Based on the hypothesis that familial cases of sex reversal are caused by mutations in an autosomal or X-linked gene in the testis determining pathway, the applicant proposes to identify such a gene by genetic linkage to polymorphic short tandem repeats (STRs) in a large family with multiple occurrences of pure or partial gonadal dysgenesis. This work should lead to a better understanding of the mechanisms of normal and abnormal sex determination.